IMPORTANT TYPES OF PKAT MATERIAL. 37 



corporated in a more or less disintegrated leaf mold, which contains 

 also the remains of herbaceous forms, ferns, and other vegetation 

 growing in a mature hardwood forest. The older matenal of the 

 layer is usually brownish black, woody, gi-anular, with ;vn abund- 

 ance of fungal hyphse. This debris characterizes the more fertile 

 area, a large proportion of which is often brought under cultivation 

 with a small expenditure for fertilizers On account of the finer tex- 

 ture of the well- weathered material and its aerated condition. 



The types of most frequent recurrence but which, at present must 

 remain without further characterization are the maple-ash -el in 

 (Acer-Fraxinus-Ulmus) type in swamps and bogs of the Central 

 and Northeastern States, often associated with oak (Quercus spp.) 

 and basswood (Tilia sp.) or with conifers, and the gum-maple 

 (Nyssa-Acer) type in the swamps of the Southeastern States. The 

 data in Table I serve to show the relative value of the European type 

 of deciduous-forest peat. 



CONIFEROTJS-rOEEST TYPES. 



" Fohrenwaldtorf." 



Reddish brown plant parts from evergreen trees or from a mixed 

 stand of conifers and deciduous forest trees which, differ much in 

 their resistance to weathering and decay agencies. The proportion 

 of fibrous or leafy material and of weathered products from shrubs 

 and herbs is quite variable. The ground mass in which, the more 

 resistant components are embedded is soft, plastic, and under mode- 

 rate draining conditions becomes granular rather slowly. In over- 

 drained deposits it dries and shrinks greatly and frequently takes 

 on the consistency of a compact substance, impervious to water, espe- 

 cially when resinous material comprises an important element in the 

 woody components. Experience indicates that coniferous peat ma- 

 terials are likely to be of low value for intensive farming purposes, 

 even several years after clearing. 



For each geographical or climatic district there are usually repre- 

 sentative tree species which establish themselves, first scattered, then 

 in a zone near the shore of lakes or valley channels, and eventually 

 cover the entire peat-land area. As they grow taller they intercept 

 a large amount of light and thus eliminate and displace the herba- 

 ceous and even shrubby undergrowth. The water of a heavy rain- 

 fall is held back sometimes to a considerable depth by the dense 

 growth and tangle of fallen vegetation, thus extending the swamp 

 conditions over adjoining areas. The larger number of trees have a 

 shallow superficial root system, which may be removed by various 

 methods of clearing, such as brushing, blasting, pulling, or bilrning. 

 The plan of " brushing out " the land, plowing shallow the first time, 

 gTadually increasing the plowed depth from year to year, and seed- 



